The pressure at which typical gas distribution systems supply gas may vary according to the demands placed on the system, the climate, the source of supply, and/or other factors. However, most end-user facilities equipped with gas appliances such as furnaces, ovens, etc., require the gas to be delivered in accordance with a predetermined pressure, and at or below a maximum capacity of the gas regulator. Therefore, gas regulators are implemented into these distribution systems to ensure that the delivered gas meets the requirements of the end-user facilities. Conventional gas regulators generally include a closed-loop control actuator for sensing and controlling the pressure of the delivered gas.
In addition to a closed loop control, some conventional gas regulators include an overpressure monitoring device. The overpressure monitoring device controls the pressure downstream of the regulator in the event that the regulator fails, thereby allowing the downstream pressure to increase to undesired levels. Accordingly, in the event the regulator fails and the downstream pressure rises above a predetermined monitor setpoint pressure, the overpressure monitoring device operates to close the valve port of the regulator valve and cut off the flow of gas to the downstream components of the gas distribution system. As demand increases, the monitoring device opens the valve port thereby allowing gas flow downstream.
FIG. 1 illustrates one example of a fluid flow regulating device as an inline gas regulator 10 having an integral inline monitoring device 12. The regulator 10 generally comprises a regulator valve body 14 and an actuator 16. The regulator valve body 14 defines an inlet 18 for receiving gas from a gas distribution system, for example, and an outlet 20 for delivering gas to an end-user facility such as a factory, a restaurant, an apartment building, etc. having one or more appliances, for example. Additionally, the regulator valve body 14 includes a valve port 22 disposed between the inlet 18 and the outlet 20. Gas must pass through the valve port 22 to travel between the inlet 18 and the outlet 20 of the regulator valve body 14, and on to the downstream portion of the gas distribution system.
The actuator 16 is coupled to the regulator valve body 14 to ensure that the pressure at the outlet 20 of the regulator valve body 14, i.e., the outlet or downstream pressure, is in accordance with a desired range of outlet or control pressures. The actuator 16 is therefore in fluid communication with the regulator valve body 14 via a downstream pressure feedback line 24 connected through the outer casing of the actuator 16. The actuator 16 includes an actuator control assembly 26 for sensing and regulating the pressure downstream of the regulator valve body 14. Specifically, the control assembly 26 includes a diaphragm 28, a piston 30, and a control linkage 32 connected via a valve stem 34 to a control element of the actuator 16, such as a valve disk 36. The valve disk 36 includes a generally cylindrical body 38 and a sealing insert 40 fixed to the valve stem 34. The body 38 and sealing insert 40 may have passages 42 therethrough extending between the surface of the sealing insert 40 facing the valve port 22 and an upper surface 44 to place the surface of a balancing diaphragm 46 in fluid communication with the upstream pressure. Configured in this manner, the balancing diaphragm 46 exerts a downward force (relative to the orientation of FIG. 1) on the valve disk 36 to counterbalance the upward force of the upstream pressure on the surface of the sealing insert 40, thereby allowing the control assembly 26 to react to the changes in the downstream pressure without undue influence from the upstream pressure.
The diaphragm 28 senses the pressure downstream of the regulator valve body 14. The control assembly 26 further includes a control spring 48 in engagement with a top-side of the diaphragm 28 to offset the sensed downstream pressure. Accordingly, the desired downstream pressure, which may also be referred to as the control pressure, is set by the selection of the control spring 48. The diaphragm 28 is operatively coupled to the control linkage 32, and therefore the valve disk 36, via the piston 30 to control the opening of the regulator valve body 14 based on the sensed downstream pressure. For example, when an end user operates an appliance, such as a furnace, for example, that places a demand on the gas distribution system downstream of the regulator 10, the outlet flow increases, thereby decreasing the downstream pressure. Accordingly, the diaphragm 28 senses this decreased downstream pressure, which allows the control spring 48 to expand and move the piston 30 and the control linkage 32 downward relative to the orientation of FIG. 1. This displacement of the control linkage 32 causes rotation of links 50 to move the valve disk 36 away from the valve port 22 to open the regulator valve body 14. With the opening of the regulator valve body 14, the appliance may draw gas through the valve port 22 toward the outlet 20 of the regulator valve body 14.
In the regulator 10 depicted in FIG. 1, the control assembly 26 further functions to vent gas passing into the upper portion of the regulator 10 in the event of a failure causing a leak in the diaphragm 28. Specifically, the control assembly 26 also includes a relief spring 52 and a failure relieve valve 54. The diaphragm 28 includes an opening 56 through a central portion thereof and the piston 30 includes a sealing cup 58. The relief spring 52 is disposed between the piston 30 and the diaphragm 28 to bias the diaphragm 28 against the sealing cup 58 to close the opening 56 during normal operation. Upon the occurrence of a failure such as a break in the control linkage 32 or links 50, the control assembly 26 is no longer in direct control of valve disk 36 and the valve disk 36 will move into an extreme open position due to the inlet flow. This allows a maximum amount of gas to flow into the actuator 16. Thus, as the gas fills the actuator 16, pressure builds against the diaphragm 28 forcing the diaphragm 128 away from the sealing cup 58, thereby exposing the opening 56. The gas therefore flows through the opening 56 in the diaphragm 28 and toward the failure relief valve 54. Upon the pressure within the actuator 16 and adjacent the failure relief valve 54 reaching a predetermined threshold pressure, the failure relief valve 54 opens to vent the gas through a vent port 60 into the atmosphere or into an attached conduit for collecting vented gas, and thereby indicating an overpressure occurrence and reducing the pressure in the actuator 16.
While the failure relief valve 54 operates to vent gas from the actuator 16, it typically does not relieve sufficient pressure to maintain the downstream pressure below the upper limit for which the regulator 10 is designed to regulate. In such situations, the monitoring device 12 operates to cut off the flow through the regulator valve body 14 until the downstream pressure is reduced after the failure of the regulator 10. In the illustrated example, the monitoring device 12 has a similar configuration as the actuator 16, and the same references with a leading “1” are used to refer to the corresponding elements of the monitoring device 12. Consequently, the downstream pressure feedback line 124 is connected through the outer wall of the casing of the monitoring device 12 to place the upper surface of the diaphragm 128 opposite the control spring 148 in fluid communication with the outlet 20 of the regulator valve body 14. When the regulator 10 functions properly, the downstream pressure remains within the desired range, and the diaphragm 128 of the monitoring device 12 does not deflect against the biasing force of the control spring 148 to close the valve port 22 with a control element of the monitoring device, such as a valve disk 136. Those skilled in the art will understand that the diaphragm 128 and the control spring 148 are configured such that the monitoring device 12 closes the valve port 22 only after the downstream pressure exceeds the upper limit of the normal operating range of pressures maintained by the regulator 10 and reaches a monitor setpoint pressure that is determined based on the load placed on the control spring 148.
FIG. 2 illustrates an example of a cantilever regulator 210 having an integral inline monitoring device 212. In the following discussion, components of the regulator valve body 214 and the actuator 216 of the regulator 210 that are similar to components of the regulator valve body 14 and the actuator 16 of FIG. 1 are identified by the same reference numerals with a leading “2,” and components of the monitoring device 212 are identified by the same reference numerals as used in FIG. 1 with the leading “1” replaced by a leading “3.” In the actuator 216, an actuator control assembly 226 includes a pivotable control arm 270 operatively coupling the piston 230 to the valve stem 234 to move the valve disk 236 as the diaphragm 228 and piston 230 move in response to changes in the downstream pressure.
The monitoring device 212 is configured with a monitor control assembly 326 having a diaphragm 328 that is a solid piece of material without an opening, and with the control spring 348 disposed on the regulator valve side of the diaphragm 328 to bias the diaphragm 328 away from the valve disk 236. The bottom of the diaphragm 328 is placed in fluid communication with the downstream pressure by a downstream pressure feedback passage 370 extending from an inner surface of the outlet 220 through the casing of the monitoring device 212 to the bottom of the diaphragm 328. When the downstream pressure increases as a result of a failure of the actuator 216, the downstream pressure forces the diaphragm 328 upward to move the valve disk 336 into engagement with the valve port 222 to cut off flow through the regulator valve body 314.
FIG. 3 illustrates an example of a first regulator 210a, with an actuator 216a as shown in FIG. 2 having a regulator valve body 414a that is not configured for attachment of a monitoring device. Instead, an external monitoring device in the form of a second actuator 216b is located upstream of the first actuator 216a to control flow through a second regulator valve body 414b. The interior of the second actuator 216b is isolated by a seal 430, but is placed in fluid communication with the downstream pressure by a downstream pressure feedback line 432 extending from the outlet 420a of the first regulator valve body 414a through the casing of the second actuator 216b. When the downstream pressure rises as a result of a failure of the first actuator 216a, the downstream pressure increase is sensed by the diaphragm 228b of the second actuator 216b to cause the second valve disk 236b to engage the valve port 422b and cut off the flow of gas from a position upstream of the first actuator 210a.
The monitoring systems described above are generally effective in monitoring the pressure downstream of the regulators and cutting off gas flow in the event of a failure of the regulators. However, drawbacks exist in certain implementations of the monitoring devices. For example, when the monitoring devices 12, 212 of FIGS. 1 and 2 are disposed in the orientation illustrated in the drawing figures, the vent ports 160, 360, respectively, are disposed above the lowest points of the casings of the monitoring devices 12, 212. As a result, moisture within the monitoring devices 12, 212 can accumulate below the vent ports 160, 360, and cannot be emptied without opening the casings of the monitoring devices 12, 212. Moisture can enter the actuators 14, 214 and monitoring devices 12, 212 via humid air. When the temperature drops, the moisture in the air condenses to liquid form and drains to the lowest point in the casing of the monitoring devices 12, 212. Moisture may also be introduced by precipitation in the form of rain or snow entering through the vent ports 160, 360. The accumulated moisture can adversely impact the performance of the monitoring device when the temperature drops and the liquid freezes, thereby impairing the ability of the diaphragms 128, 328 and control springs 148, 348 to respond to changes in the downstream pressure. Therefore, a need exists for a monitoring device providing a vent port proximate the lowest point of the monitoring device regardless of the orientation of the monitoring device.
The upstream monitoring device of FIG. 3 is also generally effective at monitoring the pressure downstream from the regulator 210a. However, having the monitoring device disposed remotely from the regulator can add expense due to the requirement for two separate regulator valve bodies to be connected along the flow path. The use of multiple bodies increases the time required and complexity of the installation of the bodies along the pipeline. The cost and complexity of maintenance is also increased. Consequently, it is desirable to provide a monitoring device having improved moisture drainage capabilities as an integral component of the regulator.